A camera device includes a photo camera, a video camera, etc., and can further include a handset, a tablet computer, a notebook computer and other mobile terminals with a front-camera and/or a back-camera, and a television set, a desktop computer and other terminal devices with an external camera.
The camera device is typically configured to acquire an image and can be further configured to present the acquired image to a user. Acquisition of an image can involve the following at least two aspects: one of the aspects relates to previewing of the image, that is, a preview image is generated before an image is taken so that the user can conveniently select an appropriate angle at which the image is taken, and the other aspect relates to taking of the image, that is, the image is taken by pressing a predetermined switch on the camera device, clicking on a predetermined area on the camera device or performing another predetermined operation. In the process above of acquiring the image, it is typically necessary to extract image details respectively from multiple acquired images to thereby compose a single image, and this may necessitate alignment of two or more images acquired at different instances of time and under different conditions (e.g., weather, illumination, and locations and angles at which the images are taken, etc.), which is referred to as image registration.